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Hello all.

Right, as I've mentioned before I am currently applying to be a pilot. I've got these practice tests to do with time/speed/distance calculations that will represent some of the tests I might face at my selection and obviously may have to use in the course of being a pilot.

Im not slow at maths, I can calculate things fairly well, its just the method of working some of these things out that I can't think of.

For example:

A man can row 50km upstream and 72km downstream in 9 hours. He can also row 70km upstream and 90km downstream in 12 hours. Find the rate of the river's current.

This I can do, its easy enough to figure out, no problems (4kph).

It's this type of question I just don't remember/know the method of figuring it out.

"Bob covers a part of the journey at 20kmph and the balance at 70kmph taking a total of 8 hours to cover the distance of 400 km. How many hours has he been driving at 20 kmph"

Its even got multiple choice, but for the life of me I can't figure out the method of detirmining that without knowing knowing how long he drove at 70, which sort of defeats the purpose of the question. Its not any adding or subtracting that gets me, its WHAT I should be calculating.

Even looking at the answers for some of these (its a whole worksheet, but its just for practice, not the actual exam), I still just can not get my head around how I should have come to the conclusion.

So, if there's somebody who's up on their calculations who could explain to me not the answer, but the way of working it out. I'm having total brain freeze over this and I'm normally fairly good at calculations, which is why this is frustrating me so much.

Can anyone help?

Matthius88 wrote:

"Bob covers a part of the journey at 20kmph

20,000 mph. Wow, that's impressive.

Arkesus wrote:

Matthius88 wrote:

"Bob covers a part of the journey at 20kmph

20,000 mph. Wow, that's impressive.

Typo. Either that or Bob is riding a meteor.
That's copied straight off the practice sheet. Nice one air force.

Matthius88 wrote:"Bob covers a part of the journey at 20kmph and the balance at 70kmph taking a total of 8 hours to cover the distance of 400 km. How many hours has he been driving at 20 kmph"

I'll point you in the right direction but let me know if you want to full thing.

Start with

20a + 70b = 400
That being 20mph at a time of A and 70mph at a time of B to cover 400m.

Now the time taken is 8 hours so
a + b = 8


go...

Matthius88, I'm assuming these are your initial aptitude tests you'll be taking?
Don't let them sweat you, not one bit. I'm far from the world's greatest mathematician and I breezed mine when I joined up. Even if you got this type of question wrong it's ok, there's plenty of others, you don't need 100%.
I wish you the absolute best though, the RAF will form a great part of your life. Just a shame you're becoming a pilot .....

A common joke, heard in many a mess:

How do you know when you're talking to a pilot at a party?
He just told you.

Lawrence wrote:

Matthius88 wrote:"Bob covers a part of the journey at 20kmph and the balance at 70kmph taking a total of 8 hours to cover the distance of 400 km. How many hours has he been driving at 20 kmph"

I'll point you in the right direction but let me know if you want to full thing.

Start with

20a + 70b = 400
That being 20mph at a time of A and 70mph at a time of B to cover 400m.

Now the time taken is 8 hours so
a + b = 8


go...

Right, Im kind of at that stage already. What I can't figure out is how you are supposed to detirmine what a and b are individually. Surely there could be a multitude of answers, depending on what a and b represent?

ARGH, confused. Most of the questions Im fine with, but there are about four of these on the sheet and they are driving me mad lol, I don't know why I can't get it.

Its not even about preparing for my aptitude tests now, its a matter of magicians pride. I HAVE to know how the "puzzle" is done.

What you need to get is b in terms of a (or a in terms of b) from one equation then substitute it for b in the other equation.

Easiest with the second one.
a + b = 8

so
b = 8 - a

put that into your first equation to get
20a + 70(8-a) = 400

Then expand out and simplify to get a; this value can then be put back into a+b=8 to get the value of b.

Cheers

You with me?

Erm right, I think Im catching up to you now.

So a is 9.2, right? Which makes the total 3 hours 12 minutes. I think.

I went through about six different answers that couldn't be right before I got to that one.

I understand the procedures your telling me, its just the bit of turning that 20a + (8-a) = 8 into actual numbers that stumps me. Its the first bit of detirmining the actual value of A from that equation. What I mean is, that first step to turning it from a to an actual value.

Algebra is not my strong point.

If its not 3 hours 12 minutes, I think its all just gone way over my head.

Van_der_Belt wrote:Matthius88, I'm assuming these are your initial aptitude tests you'll be taking?
Don't let them sweat you, not one bit. I'm far from the world's greatest mathematician and I breezed mine when I joined up. Even if you got this type of question wrong it's ok, there's plenty of others, you don't need 100%.
I wish you the absolute best though, the RAF will form a great part of your life. Just a shame you're becoming a pilot .....

A common joke, heard in many a mess:

How do you know when you're talking to a pilot at a party?
He just told you.

And yeah, this is practice for my initial tests. The rest of the practice ones I've done, like lateral thinking, spacial awareness, multi-tasking, I do great on. Its just these damn things lol.

Oh and I have a few mates that have been airmen or gunners in the RAF Reg, so Im being tutored in how to not be *that* pilot

you got the right answer but i'll run it in full so you can see where I'm going

20a+70b=400
a+b=8

so b=8-a

substituting gives
20a+70(8-a)=400

Expand to
20a+560-70a=400

simplify to
-50a=-160

becomes
50a=160

so
a=160/50=3.2

therefore
b=8-3.2=4.8

to confirm
20(3.2)+70(4.=64+336=400

All maths is algebra, try not to be daunted by the use of letters instead of numbers, a number is just a letter that represents a value that you don't have to think about!

Look up simultanious equations if you need to know more.

Interesting post,

rather you than me.

if you need help with your 5 times tables please let me know

Good luck with your application. I'm going to put my 'bad guy' hat on for a second, but it's not really _that_ bad. For the record, I used to be a flight instructor (and therefore a commercial pilot).

If you are going for flight crew I would _strongly_ suggest that you get some tutoring in maths. Simultaneous equations (the problems with which you are having, er, problems) are at the simpler end of maths, and if that sort of lateral (or abstract) thinking is hard for you, then I think you will have more problems down the line, which may threaten your path to flight. Go to the local university and scan the notice boards for a maths tutor (or put a sign up asking for one). Expect to pay around 25 pounds an hour, but it will be worth it in the long run.

In the early stages of flight training there are a lot of calculations that need to be done swiftly, and if you have spent some time getting the skills before you get into the cockpit you will be at an advantage.

Again, good luck and I hope you get your wings.

Ian

IanKendall wrote:Good luck with your application. I'm going to put my 'bad guy' hat on for a second, but it's not really _that_ bad. For the record, I used to be a flight instructor (and therefore a commercial pilot).

If you are going for flight crew I would _strongly_ suggest that you get some tutoring in maths. Simultaneous equations (the problems with which you are having, er, problems) are at the simpler end of maths, and if that sort of lateral (or abstract) thinking is hard for you, then I think you will have more problems down the line, which may threaten your path to flight. Go to the local university and scan the notice boards for a maths tutor (or put a sign up asking for one). Expect to pay around 25 pounds an hour, but it will be worth it in the long run.

In the early stages of flight training there are a lot of calculations that need to be done swiftly, and if you have spent some time getting the skills before you get into the cockpit you will be at an advantage.

Again, good luck and I hope you get your wings.

Ian

Thanks for the well wishes. Normally Im not this bad at maths, its just been a long time since I've done anything like this and the method had totally escaped me. I fully intend to brush up on these skills though, the AFCO gave us a huge list of practice questions. But yeah, I apreciate the advice.

And Lawrence, you my friend are a star. Now I see where I was bumbling, once I got it, I've done the other questions in that section no problem. Just needed to sweep out the cobwebs.

Thanks my friend!

THat's my maths degree going to good use there then!

Lawrence wrote:THat's my maths degree going to good use there then!

For the 1st time?